Frequency modulated continuous wave (FMCW) radar, sometimes known as continuous wave frequency modulated (CWFM) radar, is a radar system capable of determining distance to a target object. In a FMCW radar system, a modulated (i.e., frequency varied over a fixed period of time) continuous wave signal is transmitted, reflected off of a target object, and received by the system. The received signal is mixed with the transmitted signal to produce a beat signal. Because the frequency difference between the transmitted signal and the received signal increases with time or distance, demodulation of the beat signal provides a distance (i.e., range) to the target object.
Continuous wave (CW) radar is similar to FMCW radar, except that the continuous wave signal transmitted is not modulated (i.e., the frequency is fixed). CW radar utilizes the Doppler shift to determine velocity information about a target object. In other words, CW radar is capable of estimating the Doppler frequency of reflected signals to determine velocity of a target object. However, a CW radar is incapable of determining the range to the target object.